TY - JOUR
T1 - Modeling the Deformation Regime of Thwaites Glacier, West Antarctica, Using a Simple Flow Relation for Ice Anisotropy (ESTAR)
AU - McCormack, F. S.
AU - Warner, R. C.
AU - Seroussi, H.
AU - Dow, C. F.
AU - Roberts, J. L.
AU - Treverrow, A.
N1 - Funding Information:
The authors thank four reviewers whose comments and suggestions led to a much improved manuscript. The research was supported under the Australian Research Council's Special Research Initiative for Antarctic Gateway Partnership (Project ID SR140300001), and the Australian Government's Cooperative Research Centers Programme through the Antarctic Climate & Ecosystems Cooperative Research Center (ACE CRC). F. McCormack was supported by an Australian Research Council Discovery Early Career Award (DE210101433). This research was undertaken with the assistance of resources from the National Computational Infrastructure, which is supported by the Australian Government and the Tasmanian Partnership for Advanced Computing. H. Seroussi was funded by grants from NASA Cryospheric Science and Modeling, Analysis, Prediction Programs. C. Dow was supported by the Canada Research Chairs Program (950-231237). This project received grant funding from the Australian Government as part of the Antarctic Science Collaboration Initiative program. Lastly, the authors acknowledge the influence of the late William (Bill) Francis Budd (1938–2022): from discussions and advice about the present work, to his long-term contributions to the studies of ice deformation, including the program of work that led to the ESTAR flow relation. RW and AT particularly want to thank Bill for many years of friendly and inspirational collaboration. Open access publishing facilitated by Monash University, as part of the Wiley - Monash University agreement via the Council of Australian University Librarians.
Funding Information:
The authors thank four reviewers whose comments and suggestions led to a much improved manuscript. The research was supported under the Australian Research Council's Special Research Initiative for Antarctic Gateway Partnership (Project ID SR140300001), and the Australian Government's Cooperative Research Centers Programme through the Antarctic Climate & Ecosystems Cooperative Research Center (ACE CRC). F. McCormack was supported by an Australian Research Council Discovery Early Career Award (DE210101433). This research was undertaken with the assistance of resources from the National Computational Infrastructure, which is supported by the Australian Government and the Tasmanian Partnership for Advanced Computing. H. Seroussi was funded by grants from NASA Cryospheric Science and Modeling, Analysis, Prediction Programs. C. Dow was supported by the Canada Research Chairs Program (950‐231237). This project received grant funding from the Australian Government as part of the Antarctic Science Collaboration Initiative program. Lastly, the authors acknowledge the influence of the late William (Bill) Francis Budd (1938–2022): from discussions and advice about the present work, to his long‐term contributions to the studies of ice deformation, including the program of work that led to the ESTAR flow relation. RW and AT particularly want to thank Bill for many years of friendly and inspirational collaboration. Open access publishing facilitated by Monash University, as part of the Wiley ‐ Monash University agreement via the Council of Australian University Librarians.
Publisher Copyright:
© 2022. The Authors.
PY - 2022/3
Y1 - 2022/3
N2 - Ice deformation dominates the evolution of ice shelf flow and the slow-moving regions in the interior of ice sheets. However, deformation may be poorly represented in large-scale ice sheet models that use the Glen flow relation, due to its questionable applicability to the steady-state flow of anisotropic ice that prevails in ice sheets, having been derived from secondary creep rates of isotropic ice. We assess the deformation regimes of Thwaites Glacier, West Antarctica, using the Glen and “Empirical Scalar Tertiary Anisotropy Regime”, (ESTAR) flow relations, the latter being derived from steady-state deformation rates of anisotropic ice. For grounded ice, the character of the flow relation determines the contribution of deformation to overall flow, with ESTAR producing greater bed-parallel shear deformation than the standard Glen flow relation. The ESTAR experiments show larger basal shear stress maxima than the standard Glen experiment because ESTAR treats the responses to simple shear stresses and compression stresses differently, reducing the role of lateral and longitudinal stresses in momentum balance. On the Thwaites Glacier Tongue, ESTAR provides the best match to observed speeds by accounting for the differing effects of stresses on ice flow. Our results highlight the importance of the numerical description of anisotropy, particularly: In regions of transition from deformation-dominated to sliding-dominated flow; in the approach to the grounding line, and across ice shelves. Given the importance of these locations in determining mass flux into the ocean, our results have implications for projections of sea level change from Antarctic ice loss.
AB - Ice deformation dominates the evolution of ice shelf flow and the slow-moving regions in the interior of ice sheets. However, deformation may be poorly represented in large-scale ice sheet models that use the Glen flow relation, due to its questionable applicability to the steady-state flow of anisotropic ice that prevails in ice sheets, having been derived from secondary creep rates of isotropic ice. We assess the deformation regimes of Thwaites Glacier, West Antarctica, using the Glen and “Empirical Scalar Tertiary Anisotropy Regime”, (ESTAR) flow relations, the latter being derived from steady-state deformation rates of anisotropic ice. For grounded ice, the character of the flow relation determines the contribution of deformation to overall flow, with ESTAR producing greater bed-parallel shear deformation than the standard Glen flow relation. The ESTAR experiments show larger basal shear stress maxima than the standard Glen experiment because ESTAR treats the responses to simple shear stresses and compression stresses differently, reducing the role of lateral and longitudinal stresses in momentum balance. On the Thwaites Glacier Tongue, ESTAR provides the best match to observed speeds by accounting for the differing effects of stresses on ice flow. Our results highlight the importance of the numerical description of anisotropy, particularly: In regions of transition from deformation-dominated to sliding-dominated flow; in the approach to the grounding line, and across ice shelves. Given the importance of these locations in determining mass flux into the ocean, our results have implications for projections of sea level change from Antarctic ice loss.
UR - http://www.scopus.com/inward/record.url?scp=85127264462&partnerID=8YFLogxK
U2 - 10.1029/2021JF006332
DO - 10.1029/2021JF006332
M3 - Article
AN - SCOPUS:85127264462
SN - 2169-9003
VL - 127
JO - Journal of Geophysical Research: Earth Surface
JF - Journal of Geophysical Research: Earth Surface
IS - 3
M1 - e2021JF006332
ER -